In some communications systems (for example, a communications system deployed early), because fewer terminal devices are served by an access network device (for example, a base station), and users have relatively low requirements on service access (for example, a data transmission rate requirement or a data transmission delay), in a configuration of a network device, coverage of a provided network (denoted as a first network for ease of understanding and distinguishing) needs to be considered preferentially, that is, it is expected that the coverage of the first network is expanded as far as possible, so that users within the wider coverage can access the network by using the same network device, and deployment and operation costs are reduced.
With popularity and development of mobile communications, a quantity of users increases continuously. In particular, in some densely populated areas, for example, a large arena, a station, and an airport, more access users need to be accommodated within relatively small coverage. Consequently, overload or the like easily occurs on the network device of the first network, and services cannot be provided normally. This phenomenon severely affects user experience.
To improve user experience, a network device capable of providing a network that has relatively small coverage (denoted as a second network for ease of understanding and distinguishing) may be disposed within the coverage of the first network, allowing terminal devices in the first network to transmit data through the second network, and further reducing load of the network device of the first network.
However, because the coverage of the second network is relatively small, constraints such as movements of the terminal devices and downlink channel quality may make the terminal devices unable to receive data sent by the network device of the second network, and user experience is affected.